Breakaway link or connector

Abstract

A breakaway link or flexible connector take the form of a short coil of wireform material having known elastic and tensile properties. The breakaway link is used to link articles in circumstances where it is desirable to have the articles separate when exposed to a pre-determined level of force. The breakaway link is a simple coil and will uncoil or release when exposed to predictable levels of force. The flexible connector is used to link articles in circumstances where some flexibility is desirable but release is not desirable. The flexible connector can be a crossed and hooked coil which will expand and/or respond predictably to a given range of force, but will resist opening until exposed to a much higher level of force. Both the breakaway link and the flexible connector are preferably constructed of known superelastic materials whose unique properties give the devices increased repeatability.

What is claimed is:  
     
       1. A breakaway link comprising: 
       a length of superelastic metal alloy wireform material having known elastic and tensile properties formed into a shape having connected concave holding portions, wherein said holding portions maintain said concavity until exposed to a pre-determined force applied in a manner and direction to separate said holding portions, and when said link is exposed to said pre-determined force, said holding portions straighten and release.  
     
     
       2. The breakaway link of  claim 1 , wherein said superelastic metal alloy wireform material is selected from the group consisting of Nickel Titanium, Copper Nickel Titanium, Iron Doped Nickel Titanium, Copper Aluminum Nickel, Copper Tin (Bronze), Copper Zinc (Brass), Copper Zinc alloyed with a few % by weight of Silicon, Tin or Aluminum, Nickel Aluminum, Iron Platinum, Manganese Copper and Iron Manganese Silicon, Nickel Titanium, Copper Nickel Titanium and Iron Doped Nickel Titanium. 
     
     
       3. The breakaway link of  claim 2 , wherein said link, upon release of said pre-determined force, will return to a configuration having concave holding portions substantially the same as said shape prior to exposure to said force. 
     
     
       4. The breakaway link of  claim 2 , wherein said shape comprises a substantially planar coil which maintains a closed shape and said coil responds to said pre-determined force by uncoiling and opening said closed shape. 
     
     
       5. The breakaway link of  claim 4 , wherein said closed shape includes a first semicircular end having a first diameter and a second semicircular end having a second greater diameter, said semicircular ends connected by two, substantially linear sides having an angular orientation to each other. 
     
     
       6. The breakaway link of  claim 4 , wherein said closed shape includes first and second semicircular ends connected by substantially linear sides which connect opposite sides of the closed shape, forming a figure-eight. 
     
     
       7. The breakaway link of  claim 4 , wherein said closed shape includes a first semicircular end having a first diameter and a second semicircular end having a second greater diameter, said ends connected by sides which curve toward the interior of the closed shape. 
     
     
       8. A flexible connector comprising: 
       a length of wireform material having first and second tips, said material being an alloy having known superelastic and tensile properties and formed into a short coil having a closed shape, a portion of said material immediately adjacent to said tips being bent substantially perpendicular to said coil, and said coil crossing itself at least once, wherein said coil maintains said closed shape until exposed to a pre-determined force applied to said coil in a manner and direction which will expand said closed shape, and when said coil is exposed to said force, said coil expands, enlarging said closed shape, and said tips each engaging a side of said closed shape forming a structure which resists the additional expansion of said closed shape.  
     
     
       9. The flexible connector of  claim 8 , wherein said closed shape is selected from a group comprising a circle, oval, pear, hourglass, figure eight, cone, triangle, circle, coil, diamond, rectangle, square and trapezoid. 
     
     
       10. The flexible connector of  claim 8 , wherein said material is a superelastic material selected from the group consisting of Nickel Titanium, Copper Nickel Titanium, Iron Doped Nickel Titanium, Copper Aluminum Nickel, Copper Tin (Bronze), Copper Zinc (Brass), Copper Zinc doped with a few % by weight of Silicon, Tin or Aluminum, Nickel Aluminum, Iron Platinum, Manganese Copper and Iron Manganese Silicon, Nickel Titanium, Copper Nickel Titanium or Iron Doped Nickel Titanium. 
     
     
       11. The flexible connector of  claim 10 , wherein, upon release of said pre-determined force, said flexible connector returns to a size and configuration substantially the same as said closed shape prior to exposure to said force. 
     
     
       12. A link arrangement comprising: 
       attachment means for securement to a load;  
       pulling means for generating a substantially linearly directed force;  
       transmission means linking the attachment means and the pulling means, for transmitting said linearly directed force through the attachment means to pull the load, and including a link member consisting of a wireform of superelastic metal alloy wound as a short coil which elastically elongates commensurate with said linearly directed force.  
     
     
       13. The link arrangement of  claim 12 , wherein the attachment means is a fishing hook, the pulling means is a fishing rod and the transmission means includes a fishing line. 
     
     
       14. The link arrangement of  claim 12 , wherein the attachment means is a chain link, the pulling means is water acting on a boat, and the transmission means includes a chain. 
     
     
       15. The link arrangement of  claim 12 , wherein the attachment means is a part of a shoe, the pulling means is an action of a foot and ankle moving within the shoe, and the transmission means includes a shoelace. 
     
     
       16. The link arrangement of  claim 12 , wherein the attachment means is a metal hook on a tie down device, the pulling means is a ratchet tightening assembly on a tie down device, and the transmission means includes a strap of a tie down assembly. 
     
     
       17. The link arrangement of  claim 12 , wherein the attachment means is a structural support member of a building, the pulling means is a motion of the building, and the transmission means includes members fixed to the support members of the building. 
     
     
       18. The link arrangement of  claim 12 , wherein the attachment means are attachment points within a force-limiting drive assembly, the pulling means is a drive member receiving rotational force, the transmission means includes a driven member and the load is work performed by said driven member. 
     
     
       19. The link arrangement of  claim 12 , wherein said metal alloy has known elastic and tensile properties and said wireform includes first and second tips, each tip of the material being free of the coil, wherein said coil responds to a pre-determined magnitude of said force by uncoiling and releasing said attachment means from said pulling means. 
     
     
       20. The link arrangement of  claim 12 , wherein said metal alloy has known elastic and tensile properties and said wireform includes first and second tips, a portion of said wireform immediately adjacent to said tips being bent substantially perpendicular to said coil, and said coil crossing itself at least once, wherein said coil responds to a pre-determined range of said force by expanding and said tips each engaging a side of said coil forming a structure which resists the uncoiling of said coil. 
     
     
       21. The link arrangement of  claim 20 , wherein the attachment means are attachment points within a shock absorbing drive assembly, the pulling means is a drive member receiving rotational force, the transmission means includes a driven member and the load is work performed by the driven member.